It frequently happens that, when a back cover of a watchcase is screwed onto the middle part thereof, one realises that, when the back cover is completely screwed in, the markings or decorative patterns, which may for example, have been stamped or etched on the face of the back cover located on the side of the watch wearer's wrist, are not suitably aligned relative to the vertical 12 o'clock-6 o'clock axis of the watch, which, of course, is detrimental to the aesthetic appearance of the watch.
While this defect in appearance may be tolerated for cheap watches, it constitutes a very inconvenient drawback for more expensive watches.
In order to overcome this drawback, the only solution known in the past consists in matching a back cover with a determined watchcase during machining, in order to ensure that once completely screwed in, the back cover is perfectly aligned with the 12 o'clock-6 o'clock axis of the watch. This solution was, however, unsatisfactory since problems were likely to occur if the original back cover of the watch was ever lost or ruined and had to be replaced by another back cover, since one could only be certain that the back cover was properly aligned with the vertical 12 o'clock-6 o'clock axis once it was screwed onto the middle part.
The Applicant of the present Application in EP Patent Application No. 01203261.1 proposed a first solution to this problem. EP-A-1278108, which disclosed a device for securing a back cover onto the middle part of a watchcase, the back cover having an external peripheral threading. This device includes an intermediate assembly including a resilient locking element and a metal element concentric to the resilient locking element, this intermediate assembly being forcibly engaged in the bottom part of the middle part of the watch and the back cover being screwed onto the metal element, such that, when the back cover is completely screwed onto the metal element, the metal element can be pivoted by sliding over the resilient locking element as far as a stop point from which the resilient locking element can pivot in turn by sliding over the middle part of the watch, which adjusts the alignment of the back cover relative to the vertical 12 o'clock-6 o'clock axis of the watch.
The solution briefly described above has the merit of providing a first response to the problem of aligning the back cover of a watchcase relative to the 12 o'clock-6 o'clock axis of the latter. In particular, it ensures that the back cover will always be suitably aligned independently of the machining characteristics of the back cover and the middle part. However, this solution implements a large number of parts and requires the use of a pin driven into the middle part and forming a stop member, which, one might fear, is not sufficiently resistant.
It is an object of the present invention to overcome the aforementioned drawbacks in addition to others by providing a device for securing a back cover onto the middle part of a watch, which has a limited number of parts and which works reliably.